DARCY P.MAYS AND STEPHEN M.EASTER in the magnitude of the dispersion effects.Hence the models involve a shift of runs from the high vari- ianudardd For structure is identified and the experimenter believes effects both the D.and l-optimal designs are highl 1 of the ommended design. sign decrease dramatically as the severity of the dis Quadratic-Cubic The smallest variances are now located at the lov and high levels of X and the low and middle levels the 出接设语遇 increases,the optimal designs (both D First-Order Model fects cases the optimal designs are highh for milder dispersion efects gre Efficiency 100.0098.4894.5978.3065.5256.52 highly efficient (both D and for mild disp effects;however,with severe dispersion effects the are very low an sign similar to the optimal designs.The results for Efficiency 10.0097.1188.3071.3450.9036.15 the interaction mo de are nearly identical,with the Interaction Model For the second-order model,both the D.and are highly in Efficiency 100.0010.00100.0089.4470.7157.74 iant to the magnitude of the dispersion effe standard nid de though they remain fairly high even for severe dis 100.0096.5588.2470.8350.3734.87 practica Second-Order Model is close to ontimal in this case 2-2-22-0-22-0-220-220-21-02 Cubic-Cubic Efficiency 85.0680.7878.2176.2376.0074.67 locations of smallest variance,while the largest vari- I-Optimal ance occurs at (1, )Pr Design the others,and like the other cases as the disper sion effects increase the optimal designs for all three Efficiency 100.0096.1991.0784.2880.3175.66 oumal of Quality Technology Vol.29.No.1.January1997 Reproduced with permission of the copyright owner. Further reprodu ithout permission. Reproduced with permission of the copyright owner. Further reproduction prohibited without permission